Add a gated Known Limitations and Deferred Work section to every package README

Every packages/*/* README now carries a canonical '## Known Limitations and
Deferred Work' section: condensed, evidence-backed bullets for consumer-visible
gaps (unimplemented features, platform caveats, MVP cuts) and consciously
postponed work (TODO/FIXME/XXX markers, RFC deferrals still open). The ten
pre-existing ad-hoc variants ('What is NOT here (TODO)', 'Deferred',
'Limitations (MVP)', 'Known limitations (tracked TODOs)', ...) are normalized
into the canonical heading.

A new doc-sync gate, scripts/verify-readme-limitations.ts, enforces the shape:
exactly one limitations-like heading per package README, byte-equal to the
canonical h2, with at least one bullet; near-miss headings fail so variants
cannot creep back. Packages with genuinely nothing to declare (dsh-brand,
dsh-timeout, dsh-subagent-mock, dsh-app-boot) are whitelisted in the script and
must NOT carry the section; whitelist entries are validated against the scanned
package set so a rename fails loud.

Wired into the doc-sync chain (package.json) and the run-gates doc-sync leaf
set; the standing rule lands in packages/AGENTS.md and the adding-a-package
cookbook; decision record in
docs/rfc/implemented/process/2026-07-10-readme-known-limitations-gate.md
(RFC index regenerated).

Also fixes two stale '(deferred)' markers claiming dsh-compact-basic is
unimplemented (the dsh-compact seam README's package table and the seam's
module doc comment).

packages/llm/llm-deepseek/README.md

@@ -34,10 +34,6 @@ Every request carries the shared attribution header from dsh-llm's `attributionH
 - **Reasoning passback rule**: on assistant turns that carried tool calls, `reasoning_content` is serialized back in history (required by the API in thinking mode); on tool-call-free turns it is dropped (ignored anyway — saves tokens).
 - Cache accounting: `cacheReadTokens` ← `prompt_cache_hit_tokens` / `prompt_tokens_details.cached_tokens`; DeepSeek reports no cache-write metric.
 
-## Limitations (MVP, documented deliberately)
-
-- `tool_choice` is not mapped (not part of the core vocabulary).
-
 ## Errors
 
 Non-2xx responses throw `LlmError` with stable codes: `AUTH` (401/403), `RATE_LIMIT` (429), `INVALID_REQUEST` (400), `SERVER` (5xx), `HTTP_<status>` otherwise. Protocol violations throw `STREAM_CLOSED` (no `[DONE]`) or `MALFORMED_RESPONSE` (bad JSON payload). Unknown wire `finish_reason`s (e.g. `content_filter`, `insufficient_system_resource`) become `finish {kind: 'error', code: <REASON>}` chunks.
@@ -45,3 +41,9 @@ Non-2xx responses throw `LlmError` with stable codes: `AUTH` (401/403), `RATE_LI
 ## Testing
 
 Unit suites run against a local `node:http` mock SSE server (no network). Real-API coverage lives in `tests/adapter.e2e.ts` (`pnpm run test:e2e`, key-gated): V4 Flash + V4 Pro across thinking enabled/disabled and both official effort levels, including the thinking+tools round trip with reasoning passback.
+
+## Known Limitations and Deferred Work
+
+- **`tool_choice` is not mapped** — not part of the core vocabulary (MVP cut, shared with the pi-ai twin).
+- **Requests use raw `fetch`, not `@cordisjs/plugin-http`** — no shared proxy/interception configuration; adoption is deferred until a second adapter wants it (`TODO(http)`).
+- **Serialization flattens user and tool-result content to text blocks** — plugin-added block types are skipped, and empty tool output crosses the wire as the literal `(no output)`.